The Making of Fire & Ice (1983)
https://www.youtube.com/watch?v=jPuTVjpuom8 - from the Returning Shadow YouTube channel (13 mins long).
The blurb:
“Fire and Ice was a 1983 animated film collaboration between Ralph Bakshi and Frank Frazetta. Because it was the most action-oriented story Bakshi had directed up until that point, rotoscoping was used, adding a sense of realism that also helped replicate the look of Frazetta’s artwork. This footage comes directly from director Ralph Bakshi’s old VHS footage.”